| | Washington, MO | Columbus, MS | United States |
| Population | 14,607 | 23,858 | 329,725,481 |
| Female Population | 53.4% | 54.6% | 50.5% |
| Male Population | 46.6% | 45.4% | 49.5% |
| Median Age | 39.6 | 39.9 | 38.4 |
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| Population - 2010 | 13,973 | 25,217 | 309,327,143 |
| Population - 2000 | 13,243 | 25,944 | 285,036,114 |
| Population - 1990 | 10,704 | 23,799 | 251,960,433 |
| Pop. 2000 to Now | 7.6% | -10.2% | 15.6% |
| Pop. 1990 to Now | 33.1% | -2.1% | 30.8% |
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| Population Density | 1,546.5 | 953.3 | 93.4 |
| Land Area | 9.4 | 25.0 | 3,531,905.4 |
| Water Area | 0.5 | 0.8 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Washington, MO | Columbus, MS | United States |
| Age 0 to 4 | 6.2% | 4.8% | 5.9% |
| Age 5 to 9 | 4.5% | 4.6% | 6.1% |
| Age 10 to 14 | 5.9% | 7.9% | 6.6% |
| Age 15 to 17 | 5.4% | 3.4% | 3.9% |
| Age 18 to 20 | 5.3% | 4.7% | 4.0% |
| Age 21 to 24 | 4.5% | 5.9% | 5.2% |
| Age 25 to 34 | 13.0% | 14.8% | 13.8% |
| Age 35 to 44 | 12.1% | 9.0% | 12.9% |
| Age 45 to 54 | 12.8% | 11.8% | 12.6% |
| Age 55 to 59 | 6.3% | 6.7% | 6.7% |
| Age 60 to 64 | 6.3% | 7.5% | 6.3% |
| Age 65 to 74 | 9.8% | 10.8% | 9.6% |
| Age 75 to 84 | 6.0% | 6.1% | 4.5% |
| Age 85 and over | 2.1% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Washington, MO | Columbus, MS | United States |
| White | 94.7% | 34.8% | 59.4% |
| Black | 0.1% | 61.0% | 12.2% |
| Asian | 0.8% | 0.6% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.5% | 0.5% | 0.4% |
| Two or More Races | 2.1% | 1.7% | 3.2% |
| Hispanic | 1.7% | 1.4% | 18.4% |
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| Marriage & Family | | | |
| | Washington, MO | Columbus, MS | United States |
| Married Population | 50.6% | 35.4% | 49.8% |
| Currently Married | 49.4% | 32.3% | 48.0% |
| Married but Separated | 1.1% | 3.2% | 1.8% |
| Single Population | 49.4% | 64.6% | 50.2% |
| Never Married | 31.7% | 43.5% | 33.8% |
| Divorced | 10.4% | 12.6% | 10.8% |
| Widowed | 7.3% | 8.5% | 5.6% |
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| Household Size | 2.39 | 2.28 | 2.60 |
| Households | 6,048 | 9,843 | 124,010,992 |
| Family Households | 3,804 | 5,263 | 80,755,759 |
| Married couple, w/children | 32.9% | 12.4% | 30.5% |
| Married couple, no children | 44.4% | 42.0% | 42.9% |
| Non Family Households | 2,244 | 4,580 | 43,255,233 |
| Single householder, w/children | 14.1% | 29.6% | 15.8% |
| Single householder, no children | 8.6% | 16.0% | 10.8% |